Introduce JsonEncode helper function

It's just a wrapper around the `JsonEncoder` class to simplify its usage.

Author: yhabteab

lib/base/json.cpp

@@ -304,6 +304,19 @@ String icinga::JsonEncode(const Value& value, bool pretty_print)
 	}
 }
 
+/**
+ * Serializes an Icinga Value into a JSON object and writes it to the given output stream.
+ *
+ * @param value The value to be JSON serialized.
+ * @param os The output stream to write the JSON data to.
+ * @param prettify Whether to pretty print the serialized JSON.
+ */
+void icinga::JsonEncode(const Value& value, std::ostream& os, bool prettify)
+{
+	JsonEncoder encoder(os, prettify);
+	encoder.Encode(value);
+}
+
 Value icinga::JsonDecode(const String& data)
 {
 	String sanitized (Utility::ValidateUTF8(data));

lib/base/json.hpp

@@ -218,6 +218,7 @@ class JsonEncoder
 };
 
 String JsonEncode(const Value& value, bool pretty_print = false);
+void JsonEncode(const Value& value, std::ostream& os, bool prettify = false);
 Value JsonDecode(const String& data);
 
 }

test/base-json.cpp

@@ -39,10 +39,14 @@ BOOST_AUTO_TEST_CASE(encode)
     "string": "LF\nTAB\tAUml\u00e4Ill\ufffd",
     "true": true,
     "uint": 23
-}
-)EOF");
+})EOF");
+
+	auto got(JsonEncode(input, true));
+	BOOST_CHECK_MESSAGE(output == got, "expected=" << output << "\ngot=" << got);
 
-	BOOST_CHECK(JsonEncode(input, true) == output);
+	std::ostringstream oss;
+	JsonEncode(input, oss, true);
+	BOOST_CHECK_MESSAGE(oss.str() == output, "expected=" << output << "\ngot=" << oss.str());
 
 	boost::algorithm::replace_all(output, " ", "");
 	boost::algorithm::replace_all(output, "Objectoftype'Function'", "Object of type 'Function'");